Conventionally, a balloon catheter is used to dilate a stenosis or the like inside a body cavity such as a vessel. Various balloon catheters are known. In one example of balloon catheters, a guidewire for guiding a balloon catheter is accommodated in and non-removable from a body of the balloon catheter for the purpose of reducing the outer diameter or like purposes (see, for example, JP-T-6-509244, U.S. Pat. No. 5,409,470 and JP-T-5-503872).
In such a balloon catheter that is integrated with a guidewire, there has been a demand for making a difference in level between a coil portion provided at a tip portion of the guidewire and a front end portion of the balloon catheter as small as possible and for forming the coil portion and the front end portion of the catheter to be curved smoothly in an integrated manner.
Specifically, a stepped portion (in particular, a stepped portion formed by an outer diameter of an end of the catheter bigger than the outer diameter of the coil portion) may be formed between the coil portion of the guidewire and the front end portion of the balloon catheter. In this case, when the balloon catheter advances in a tortuous vessel, such a stepped portion may get stuck in an inner wall of the vessel or in a strut (a support forming meshes) of an indwelling stent or like disadvantages may be caused, which results in reduced crossability of the balloon catheter.
In the techniques disclosed in JP-T-6-509244 and U.S. Pat. No. 5,409,470, a connection structure is provided between a rear end of a coil part of a guidewire and a front end portion of a balloon catheter body. Thus, this is considered to be effective to a certain extent in reducing the difference in level between the coil part of the guidewire and the front end portion of the balloon catheter.